chore: Make example stacks use new major version

[lym953]

What does this PR do?

1. Make the 6 example stacks under examples/ use the new major version by changing dependency files and imports.
2. Make the Python stacks at integration_tests/stacks_python use the new major version
3. Delete code that references APIs that no longer exist.
4. Delete examples/step-functions-go-stack/ddcdkconstruct folder, which was for local testing and was added by mistake.

Motivation

Testing Guidelines

1. All the six example stacks were deployed successfully: {Node.js, Python, Go} $\times$ {Lambda, Step Function}
2. Integration test (scripts/run_integration_tests.sh) was successful.

Additional Notes

Types of Changes

• Bug fix
• New feature
• Breaking change
• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR contains breaking changes that are documented in the description
• This PR introduces new APIs or parameters that are documented and unlikely to change in the foreseeable future
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests
• This PR collects user input/sensitive content into Datadog